Alright, here we go:
In the presence of a FULL khalifate there can be a death penalty applied for one who leaves the fold of Islam without an external influence (i.e. propaganda etc). The death penalty can ONLY apply IF and ONLY IF the person announces it publically. It does not apply to a woman, or a child etc. In the case of the penalty it can ONLY be applied on a case by case basis by a full ruling body. Because of that it makes it very rare for it to happen and thus pretty much does not apply. Furthermore there is NO full khalifate on Earth, therefore the law cannot be upheld either. If I recall there has only been once incident of a death penalty being warranted and that was for Salman Rushdie.
So, whilst you are right in the fact that the death penalty IS there, there is not enough backing on the penalty for it to even be applied in todays day and age. The same way there is no backing for anyone changing religion and having suffer a death penalty (which used to apply to Christians and Jews as well). Now in the case of Mr Rushdie, the only reason I can think that the death penalty applied was because all of the ruling bodies on Earth unanimously agreed and he did FAR more than just leave a religion.
This is the best that I can explain with my limited knowledge. I hope it helps?
@kennylmao
Here we go. Here is some wisdom directly from the horse's mouth that proves otherwise. When Mohammad was writing the Quran, he was told by some of his followers that some of his teachings were in conflict with others. His response was found in 2:106:
Whatever a Verse (revelation) do We {Allah} abrogate or cause to be forgotten, We bring a better one or similar to it. Know you not that Allah is able to do all things? What he means here is that his "god" was capable of doing all things, even changing his mind when it suits him.
Taking that a step further, when the Quran was compiled into book form, all of Mohammad's writings were ordered from the longest to the shortest without any regard to historical and literal context. Take a look at Quran 50:45 and Sura 109, both "revealed" in Mecca:
50:45. We know of best what they say; and you (O Muhammad) are not a tyrant over them (to force them to Belief). But warn by the Qur’an, him who fears My Threat.109:1. Say (O Muhammad to these Mushrikun and Kafirun): “O Al-Kafirun (disbelievers in Allah, in His Oneness, in His Angels, in His Books, in His Messengers, in the Day of Resurrection, and in Al-Qadar {divine foreordainment and sustaining of all things}, etc.)!
109:2. “I worship not that which you worship,
109:3. “Nor will you worship that which I worship.
109:4. “And I shall not worship that which you are worshipping.
109:5. “Nor will you worship that which I worship.
109:6. “To you be your religion, and to me my religion (Islamic Monotheism).
Then there is this passage, which was "revealed" after Mohammad's army took over Medina and were still venerable:
2:256. There is no compulsion in religion. Verily, the Right Path has become distinct from the wrong path. Whoever disbelieves in Taghut {idolatry} and believes in Allah, then he has grasped the most trustworthy handhold that will never break. And Allah is All-Hearer, All-Knower.
Then comes the "verse of the sword", which was revealed later in Mohammad's life:
9:5. Then when the Sacred Months (the 1st, 7th, 11th, and 12th months of the Islamic calendar) have passed, then kill the Mushrikun {unbelievers} wherever you find them, and capture them and besiege them, and prepare for them each and every ambush. But if they repent and perform As-Salat (Iqamat-as-Salat {the Islamic ritual prayers}), and give Zakat {alms}, then leave their way free. Verily, Allah is Oft-Forgiving, Most Merciful.
Having been revealed later in Muhammad's life than 50:45, 109, and 2:256, the Verse of the Sword abrogates their peaceful injunctions in accordance with 2:106. Sura 8, revealed shortly before Sura 9, reveals a similar theme:
8:39. And fight them until there is no more Fitnah (disbelief and polytheism: i.e. worshipping others besides Allah) and the religion (worship) will all be for Allah Alone [in the whole of the world]. But if they cease (worshipping others besides Allah), then certainly, Allah is All-Seer of what they do.8:67. It is not for a Prophet that he should have prisoners of war (and free them with ransom) until he had made a great slaughter (among his enemies) in the land. You desire the good of this world (i.e. the money of ransom for freeing the captives), but Allah desires (for you) the Hereafter. And Allah is All-Mighty, All-Wise.
9:29. Fight against those who believe not in Allah, nor in the Last Day, nor forbid that which has been forbidden by Allah and His Messenger and those who acknowledge not the religion of truth (i.e. Islam) among the people of the Scripture (Jews and Christians), until they pay the Jizya with willing submission, and feel themselves subdued.
9:33. It is He {Allah} Who has sent His Messenger (Muhammad) with guidance and the religion of truth (Islam), to make it superior over all religions even though the Mushrikun (polytheists, pagans, idolaters, disbelievers in the Oneness of Allah) hate (it).
Taking 2:106 into account, this means that every "revelation" that Mohammad had in his later life is meant to supersede all of his early teachings about peace.